Week 6 Flashcards
(22 cards)
What are between-groups designs
Different groups of people in each experimental condition
What are between-groups designed also called?
Unrelated samples, independent samples/measures, uncorrelated samples/measures, between-participants, between-subjects
What are the advantages and disadvantages of between-groups designs
A: There are no problems with order effects. No need to duplicate and match materials
D: Individual differences and experimental groups. Need more participants. Issues with power.
What is a repeated measures design
Same group of participants performing in all experimental conditions.
What are repeated measures designs also called?
related samples, dependent-samples/measures, correlated-samples/measures, within-subjects, within-participants, within-groups
What are the advantages and disadvantages of repeated-measures designs
A: Elimination of permanent or chronic individual differences. Fewer participants required.
D: Order effects, Carry-over effects
What is the yerkes-dodson arousal curve for?
it shows the optimal level that people perform at relating to arousal level. When people are under or over stimulated performance will decrease.
What are the experimental research advantages of using a repeated measures design
Each level of the independent variable is experimentally manipulated. The sequence in which the levels of the independent variable are given can be varied.
What are the longitudinal (sequence-based) research advantages of a repeated measures design
Each level of the independent variable normally represents a quantitative change. The order of the sequence is fixed. Examples: grade level of child, number of practice trials, number of treatment sessions.
What two ways is power enhanced by a repeated measures design?
- Reduced variability due to individual differences. (As the participant is the same at each measurement, it follows that individual differences will be the same, thus error from this source is reduced).
- More observations per participant. (More observations will help balance out random error)
List advantages of repeated-measures designs
Increased efficiency (fewer participants for same amount of power), Many variables in psych can only be studied in repeated measures, longitudinal or sequence-based research (practice/training, age-related changes, and treatment effects over time)
List order effects related to the disadvantages of repeated measures designs
Practice effects, Fatigue effects, other psychological effects (reducing or increasing anxiety), treatment carryover effects (lingering effects of alcohol or other drugs, using strategies learnt in previous conditions), sensitisation effects (participant behaviour changes as they think they know what the study is testing) `
What is complete counterbalancing
Each condition in our experiment follows and is preceded by every other condition in an equal number of times
What are permutations
Number of orders possible
How to calculate permutations for counterbalancing?
K x (k-1) x (k-2) x …. 1
What is the Latin Squares Design
Used for incomplete counterbalancing.
Each condition will occur in each spot once (condition a was in 1st, 2nd, and 3rd only once).
What is a matched-subjects design
A compromise of between-groups and repeated-measures design.
What is the procedure of a matched subjects design
- Measure participants on variables that are known to affect the DV
- Match participants on these key variables (create equivalent pairs)
- Randomly assign matched participants to experimental groups
Explain matching in ‘sets’
Set size is equal to the number of conditions. (If there are 4 conditions we need to recruit in sets of 4 matched on the desired attributes)
With 2 match criteria (E.g., Artistic ability and hand dominance) we need 4 sets:
(4 sets x 4 conditions = 16 participants)
With 3 match criteria we need 8 pairs:
(8 sets x 4 conditions = 32 participants)
How is a matched design analysed
It is analysed as if it were a repeated measures study. (data from matched participants are organised as though the data from a matched pair came from a single participant)
Using a paired samples t-test.
List advantages of Matched designs
Increases statistical power (sensitivity to group differences)
Does this by trying to minimise differences within group error.
No sequence effects
Can improve internal and external validity
List disadvantages of matched designs
Participants may guess the purpose of the experiment (damaging construct validity)
If your matching variables are no good
Matching is difficult
Matching gets more difficult as: The number of matching variables increases, Matching is done on continuous variables, The number of conditions increase
Time and energy
Participants without appropriate matches cannot be used
